The invention relates to a grounding contact for transmission of currents between fixed vehicle elements of a rail vehicle, such as an electric, diesel-electric or diesel-hydraulic locomotive or traction and traveling vehicle, and its rotating wheel axle, including at least one contact element, such as carbon brushes, which are acted upon by pressure in the direction of the wheel axis, which lies or lie on a contact surface containing or including carbon material originating indirectly or directly from the wheel axle, whereby at least the contact element is subjected to pressure through a flat element in the direction of the contact surface.
Operating and/or signal currents of rail vehicles can be guided through axle shafts and axle wheels to the rails, and therewith to the source of energy. The transmission from the fixed vehicle parts to the rotating axles takes place for this purpose with special current bridges which are usually designated as reverse current/grounding contacts.
The roller bearings of the axles can lie in the useful current circuit or parasitic current circuit. In order to protect them against passage of current and consequently against destruction, reverse current/grounding contacts must form a low resistance bridge. With a tension available through the bearing from, for example, 0.1-1 V (fritting voltage), the flow of current through the bearing begins. Associated with an irregularly rising amount of current, the value of the transition tension subsequently drops to ca. 0.5 V.
Reverse current/signal current/grounding contacts should produce a good and secure electric connection between the reverse current connection on the vehicle and the wheel axle on a defined current pathway in all operating situations of the vehicle. Furthermore, it must be assured that a constant transition resistance exists during signal transmission.
With a grounding contact known from DE-OS 1 953 043, a carbon brush is supported spring-prestressed, but not pivoting, in a housing originating on an axle of an electrical rail vehicle, which is braced in relation to a rotating contact disk. Here the carbon brush can either be pressed against a contact plate by means of a compression spring, or this can be pressed against the carbon spring by means of a tension spring. When using a compression spring, this can likewise originate from a disk which is directly connected with the axle.
A cleaning block not designed as a grounding contact is known from DD 81 136 which can be pressed on the running surface of the running surface of the wheel of a rail vehicle by means of a hydraulic or pneumatic cylinder.
An electric rail vehicle with a rubber-sprung driving wheel is known from CH 176 524. Here the work current is derived through a carbon brush which is pressed on a wheel tire such that the carbon brush at the same time acts as a cleaning block for the running surface of the wheel tire.
A further grounding contact is described in EP 0 582 888 A1. Here the contact surface on which the carbon brush is supported is made of or contains carbon material. In this way, there results, among other things, the advantage of a reduction of wear and tear in relation to other grounding contacts.
A grounding contact representative of its type can be gathered from EP 0 805 089 A2 (U.S. Pat. No. 5,924,871). Here the contact element is acted upon by means of a device filled with fluid or a liquid material. On the contact element side, the fluid is bounded by a membrane owing to which the advantage exists that the device acted upon by pressure lies on the contact element or elements such as carbon brushes even when area-wise differences in wear and tear are present such that the contact elements for their part lie on the contact surface to the necessary extent and flat. In connection with construction in this regard, it should be assured that the fluid or the material capable of flowing is enclosed such that the requisite action of pressure takes place.
Underlying the present invention is the problem of perfecting a grounding contact of the type mentioned at the beginning such that it can be guaranteed with simple construction measures and light construction with respect to weight that the contact elements lie upon the contact surfaces to a sufficient extent, whereby the sealings required according to the state of the art are to be avoided.
In accordance with the invention, the problem is solved in that the flat element is an elastic layer of elastomer material arranged on a mounting. At the same time, the flat element spans a plane which runs parallel or approximately parallel to the contact surface itself. With the elastomer material, it can, for example, be rubber sponge.
In particular, the flat element has the shape of a disk element which completely or almost completely covers the contact elements.
The mounting for the flat element itself is a pot-shaped constructed pressure plate whose circular edge encloses the flat element edgewise, and has recesses.
It is especially provided that the pressure plate in section is H-shaped, whereby the pressure plate consists of a peripheral wall forming a hollow cylinder and a partition running at a distance to its front walls, which is the support of the elastic layer. On the opposite side, spring elements can operate in the known manner in order to press the pressure plate with the elastic layer together with the contact elements onto the contact surface to the necessary extent.
Even if the elastic layer is preferably a disk element, this can if necessary be composed of segments, preferably in the form of circular sectors.
The elastic layer itself should have a hardness of preferably 20-60 Shore A, especially between 40 and 50 Shore A. Temperature resistance between xe2x88x9245xc2x0 C. and +250xc2x0 C., water tightness, resistence to oils, fats and paints, resistance to aging and electrical non-conductivity can further be mentioned as additional preferred material characteristics of the elastic partition. The E-module comes to ca. 40 N/mm2. Silicon should be mentioned as an especially suitable material, which is tempered if necessary.
Owing to the fact that the mounting with the elastic partition can be constructed relatively lightly without having to allow for losses with respect to functional capacity, there results an exceptionally rapid reaction to the case of when a vehicle is tilted, so that the desired grounding is always assured.
Further details, advantages and features of the invention emerge not only from the claims, the features to be inferred from this (in isolation and/or in combination), but also on the basis of the description below of a preferred embodiment to be gathered from the drawings, wherein: